1. Field of the Invention
The invention relates to a method for producing continuous tooth flank corrections on hypoid bevel gears, for example, on ring gears, with the teeth of the hypoid bevel gear being machined in a single operation on the concave and convex flanks by plunge-cut grinding or plunge milling using a CNC-controlled bevel gear cutting machine.
Advantageously, the method of the invention preferably may be performed on a universal, completely CNC-controlled bevel gear grinder made by the Klingelnberg Company, the WNC 30. This machine has five controlled axes, the workpiece rotational axis, which is required during hobbing to produce the correct tooth shape and in Formate.RTM. ring gear grinding for separation, together with a C-axis for the machine base angle and three coordinates X, Y, and Z. The second grinding wheel is not required for the process unless a separate rough and smooth grinding wheel are used. By plunging the grinding wheel in the axial direction, the two tooth flanks of the gash are machined in a single step. For this purpose the machine is set to a machine base angle .delta.. This produces an uncorrected ring gear toothing. For example, a ring gear can be produced with a constant tooth height as well as a ring gear with a tapering tooth height.
2. Description of the Prior Art
In the manufacture of so-called Formate.RTM. (registered trademark of Gleason Works, Rochester, N.Y. USA) ring gears, both flanks of the ring gear are final-machined on the concave and convex sides by plunge-cut grinding and plunge milling. Modifications of the toothing, in other words, changes in the supporting pattern, previously were performed exclusively on the pinion, including corrections to the lengthwise camber and pressure angle, which were previously possible on the bevel gear.
For some time it has been possible to make corrections to the ring gear using the so-called "flared-cup method" of the Gleason Company. In this process, the grinding wheel does not plunge in a single step, and machines the flanks by surface contact, but as a result of an inclination of the grinding wheel axis relative to the gash, linear contact results in the direction of the height of the tooth, and the lengthwise shape of the tooth is created by additional movements of the grinding wheel relative to the gear. As a result of the linear contact between the grinding wheel and the workpiece in the "flared-cup method" in contrast to areawise contact in pure Formate.RTM. grinding, corrections can be made on the tooth flanks. The method has the disadvantage, however, that a cumbersome machine adjustment calculation is required and time is lost as a result of the linear contact in the machining of ring gears.
The bevel gear grinder shown in FIG. 1 is completely CNC-controlled and has five controlled axes, namely, the workpiece rotational axis B that is required during hubbing to produce the correct tooth shape and in Formate.RTM. ring gear grinding for separation, as well as the C axis for the machine base angle and the three coordinate axes X, Y, and Z.